1. Field of the Invention
The present invention relates to a broadband RFID label (tag) antenna; a dual mode is applied for conquering problems brought about by the narrowband of the microstrip antenna; one mode is formed by symmetrical full-wave resonance, and the other mode is formed by unsymmetrical full-wave resonance; thereby, the antenna could be bended and miniaturized; a preferable impedance match is achieved between the antenna and a chip; the present invention could be applied in a surface of a metal object.
2. Description of the Related Art
Existing RFID is bended for miniaturizing the integral area of the label antenna so as to decrease the manufacturing cost. Wherein, a back of a radiation body is added with metal, and a microstrip antenna is contributed. In order to conquer problems of narrowband brought about by the microstrip antenna, a first plane drilling hole of the antenna and the metal disposed at the back would be connected by copper posts. Thereby, the antenna easily results in effects of broadband.
An R.O.C. patent publication No. TW200905973 showing “RFID TAG AND METHOD FOR MANUFACTURING RFID TAG” provides an RFID tag with independently and easily adjustable (controllable) resistive components and reactive components of impedance for achieving miniaturization easily. Therefore, the RFID tag of the invention comprises an antenna conductor, a first feed electric conductor for electromagnetic induction coupling the antenna conductor and an annular second feed electric conductor electrically connecting to the first feed electric conductor.
Another R.O.C. patent publication No. TW200908204 is a type of “RFID TAG AND ITS MANUFACTURING METHOD” where one of the goals is to provide an RFID tag capable of preventing gain decrease and of easy adjustment to match the chip it carried. The RFID tag comprises a ring antenna pattern that connects to an electrical contact of the chip; and a conducting element that conducts to a portion of the antenna pattern. Concurrently, a coupling part is introduced by a coupling portion and a section of a radiation metal wire. A tuning part is electrically connected to the connecting element.
Another R.O.C. patent publication No. TW200913377 showing “RFID TAG AND METHOD FOR MANUFACTURING RFID TAG” provides a wireless tag corresponding to metal having a wider passband (frequency to communication distance) characteristic than before is realized. The wireless tag comprises a first oscillator pattern having a chip connection portion to which a chip is connected and an inductance portion for adjusting impedance match with the chip and a second oscillator pattern to which power is supplied by electromagnetic induction combination via the inductance portion.
Another R.O.C. patent No. 1306218 showing “RFID TAG FOR METAL” provides a dielectric base attached with an antenna having electrically conductive materials. A radio communication IC is further electrically connected to the antenna. The antenna has a radiation portion and a grounding portion. The radiation portion is formed on a surface of the dielectric base, and the grounding portion is formed on a back of the dielectric base. The complete antenna achieves a resonance mode or a radiant mechanism. The radio communication IC is electrically connected between the radiation portion and the grounding portion. Thereby, this structure allows the RFID on metal objects to be precisely read or written in accordance with a reader.
Another R.O.C. patent No. 1315053 showing “RFID TAG” provides an antenna having a dipole conductor pattern, and an integrated circuit transistor connected to the RFID tag. The RFID tag further has an adjusting part including at least one adjusting pattern that is connected to the conductor pattern, so that the antenna could be suited to an environment, and a label part. A direction of operation while using the adjusting part indicates the label part.
Afore disclosures have shortcomings as follows:
1. The radiation body has limiting area, thereby incurring reduced radiation efficiency and shortened transmission distance.
2. The existing RFID tag is weak in restraining metal interference, hence resulting in larger return loss.
3. The antenna is restricted since the radiation body provides unsatisfactory area; thus, the bandwidth is narrower.
4. No dual mode and double resonance are provided, so the application is further limited.
Accordingly, although the existing RFID tag is able to provide basic radio communication in accordance with a certain bandwidth, the radiation efficiency, the transmission distance, the interference restraining ability, and the entire design are incapable of being satisfactorily applied in practice due to afore defects.
As a result, the existing RFID tag needs amendment for providing better choices and meeting the current industrial trend.